I went to the Naschmarkt am Dom tea-house and sweets store 4 times in 2 months because it is the BEST place to go for a snack or a tea-time. The place is incredibly welcoming and the waitresses are all extraordinarily friendly! Everytime I went there, the pastries were different and sooooo good looking that I always take one with a marvellous hot chocolate (yes, the ones with a chocolate block at the end of a wood spoon!) that you let a bit melt before drinking. All the cakes seem natural and hand made and I am broken-hearted to leave Frankfurt just because of this place, because my studies are over... As, it is very central in the Altstadt of Frankfurt (and just next to the biggest church), you cannot miss it and you would definetely go there if you visit the Römerberg. GO THERE!